Sound motion picture reproducing apparatus



. Nov. 14, 1939. s. MORSE 2,180,014

SOUND MOTION PICTURE REPRODUCING APPARATUS Filed Oct. 25, 1936 AMPLIFIER LOUD SPEA ATTORNEYS.

OUTLET TO Patented Nov. 14, 1939 PATENT OFFICE SOUND MOTION PICTURE REPRODUOING APPARATUS Richard's, Morse, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application October 23, 1936, Serial No. 107,254

3 Claims.

This invention relates to the reproduction of sound. More particularly it relates to the reproduction of sound in connection with motion pictures.

During the projection of motion pictures, it is sometimes desirable to describe verbally to the audience some particular feature, especially in the case of public speakers who illustrate or supplement their lectures by means of motion pictures (either silent or sound). If a sound motion picture projector is used to project silent films, it would be decidedly advantageous to allow the speaker to address his audience through the amplifying circuit and the loud speaker of the projector system. Even when sound films are being projected, occasions arise when it is desirable to interrupt the normal output of the sound record and, to substitute pertinent comments or special announcements.

Obviously, to avoid confusion, the normal sound sequence should be silenced during the interlocution. Depending on the circumstances, it mayor may not also be desirable, at that time, to interrupt the pictures, or to project a still from a single frame.

It is an object of this invention to provide a method and means which will permit the output of an auxiliary microphone to utilize the amplifier and loud speaker of a sound motion picture projector. I

It is a particular object of this invention to arrange an electrical circuit whereby the normal sound reproduction is interrupted when the auxiliary microphone circuit is completed. The simultaneous interruption of the motion pictures (e. g., to project a still) when desirable may easily be controlled by the operator of the projector or by any suitable remote control.

As pointed out above, this invention will be particularly useful when motion pictures of the silent type are being projected by a sound projector.

Further objects and advantages of this invention will be apparent from the following description when read in connection with the accompanying drawing in which:

Figure 1 shows one particular form which the invention may take.

Figures 2 and 3 schematically show the construction of two mechanisms suitable for use as switch It), Figure 1. 7

Figure 4 shows an alternative switching arrangement which may be used as described below in a modified form of the circuit shown in Figure 1.

In Figure 1, a motion picture film I3 bearing a sound track I2 is moved in a well known manner between a projection lamp 28 and a projection lens 29 to project the pictures in the usual Way. The film band I3 is also moved so that the sound 5 track I2 modulates the light from an exciter lamp Ii. The modulated beam of light is received by a photoelectric cell I4 which with its accompanying circuit and loud speaker transforms the modulated luminous energy into modu- I0 lated electrical energy, and finally into audible sound in the well-known manner. In the circuit, the alternating component of the output of the photoelectric cell I4 is transmitted through 4 a condenser I5 to the grid of a thermionic am- 1'5 plifier tube I6. The potential for the photoelectric cell I4 is supplied from a source I9 through resistances I! and I8. An electrical switch 20 comprising electrodes 2|, 22, 23, and 24 is connected, as shown, in the grid circuit of the tube 20 I6 in series with a grid leak resistance 26. An auxiliary microphone 25 is connected between ground and the electrode 24 of the switch 2|].

In normal operating position, the switch 20 is set so that electrodes 22 and 23 are in contact, 25 and electrodes 2| and 24 are entirely disconnected. Thus, the power from the source I9 is supplied to the photoelectric cell I4, the grid leak 26 is connected directly to ground and the auxiliary microphone 25 is disconnected from the 30 circuit.

The switch 2|] is arranged so that it has only one alternative position. In this alternative position, the electrodes 2| and 22 are connected and the electrodes 23 and 24 are connected. Thus, the source of potential I9 is shorted, the resistance I8 being provided to prevent any damage being done thereby. Also, the grid leak 26 is no longer directly connected to ground, but is in series with the microphone 25. 40

Hence, the output of the microphone 25 is substituted for the output of the photoelectric cell I I and is supplied to the grid of the tube I6, the output of which in turn operates an amplifier and loud speaker system 21.

This switch 20 may be designed in various ways. Two satisfactory and convenient arrangements are shown in Figures 2 and 3.

In Figure 2, the electrodes 2| and 23 are mounted rigidly on a base 3|. The electrodes 22 and 50 24 are rigidly connected by a member 32 which is pivotally mounted on the base 3|. A spring 34 mounted on the base 3| holds the member 32 so that the electrodes 22 and 23 are normally in contact. Pressure exerted on a button 33 which 55 is mounted on the member 32 compresses the spring 34 to disconnect electrodes 22 and 23, and to connect electrodes 23 and 24- and electrodes 2| and 22, respectively as discussed above.

Figure 3 shows a jack type connector adapted to operate as the switch 20. A plug 36 carries electrodes 24 and 31 which are connected to the microphone 25. The plug 36 may be inserted between spring members which comprise the electrodes 22 and 23. Normally the electrodes 22 and 23 are in contact as shown. When the plug 36 is inserted, electrodes 22 and 23 are separated and electrode 22 is moved into contact with electrode 2|. Insertion of the plug 36 also brings the electrodes 23 and 2d and the electrodes 22 and 3! into contact to connect the microphone 25 between the grid leak resistance 26 and ground as described in connection with Figure 1.

Referring back to Figure l, the sound track I 2 may be carried on the film as shown or it may be of the sound-on-disk type. If it is of the sound-on-film type, it may be either variable width or variable density. The circuit used with the photoelectric cell l4 may be of any suitable type, only one of which is shown. The introduction of the microphone 25 into the circuit and the interruption of the audio output of the photoelectric cell M may be accomplished in a number of ways. For example, the exciter lamp Il may be extinguished during the interlocutien instead of shorting the potential source 19.

One suitable form of switch for accomplishing this is shown schematically in Figure 4. Electrode 2! has been eliminated in this case and two electrodes M and 42 have been introduced. These latter two electrodes are connected in series with the exciter lamp II and act as a switch therefor. In normal operating position electrodes 22 and 23 and electrodes 4| and 42 are in contact. When the switch is actuated to connect the microphone in the circuit it opens the ground connection at contacts 22 and 23 and separates the contacts il and 42 to open the exciter lamp circuit. Thus the exciter lamp is extinguished, the photoelectric cell I4 is darkened, and the tube l5 receives only the output of the microphone 25.

In Figure 1, the tube [6, shown as a triode, is merely to represent suitable means for receiving and transmitting the modulated electrical energy from the alternative sources. Other satisfactory arrangements will immediately suggest themselves to those skilled in the art.

Having thus described this invention, I wish to point out that it is not limited to the specific forms shown but includes those modifications falling within the scope of the appended claims.

I claim:

1. In a system for reproducing sound from a photographic sound record, a photo-cell the illumination of which is controlled by said record, an amplifier including a vacuum tube provided with a grid. means including a grid leak resistance for impressing potential variations upon the grid corresponding to the illumination of said cell, a microphone, and switching means operative to disconnectsaid means and to connect the microphone in series relation with said grid resistance, whereby the microphone is in circuit to control the input to said amplifier.

2. In a system for reproducing sound from a photographic record having variations characteristic of the sound recorded thereon, means for transforming the sound record variations into electrical current variations, said transforming means consisting of a photoelectric cell and a source of potential therefor, means for translating the electric current variations into potential variations, an amplifier connected to said translating means, means for side tracking the power of said source of potential away from the photoelectric cell, a microphone, and a two position switch so arranged that in one position the source of potential is disconnected from the side tracking means and the transforming means is connected to the translating means, and in the other position the source of potential is connected to the side tracking means and the microphone is connected to the translating means.

3. Apparatus for the reproduction of sound motion pictures comprising a motion picture film bearing an optical sound record, an exciter lamp to illuminate said sound record, a loud speaker, a photoelectric cell arranged to receive light modulated by said sound record and connected to operate the loud speaker through a suitable electrical circuit, a microphone and means movable to extinguish said exciter lamp thereby rendering said photoelectric cell inoperative and to connect said microphone to the loud speaker circuit.

RICHARD S. MORSE. 

